Process for combating fungi

ABSTRACT

Compositions containing certain surface active agents are used to combat overwintering fungal diseases in plants. Particularly perferred surface active agents are condensates of alkyl phenols or straight or branched chain fatty alcohols with from 3 to 50 moles of ethylene oxide.

This invention relates to a process for combating fungi. Moreparticularly it relates to a process for combating overwintering fungaldisease, for example the mycelium and spores of fungi harboured by treesduring their winter dormancy period and giving rise toactively-spreading fungal disease when the tree resumes active growth inthe following spring and summer.

It has been known for some years, for example, that the successfulperennation of the apple mildew fungus, Podosphaera leucotricha, is dueto its ability to survive the winter in vegetative and fruiting buds. Inthe spring and early summer these buds give rise to diseased tissues(primary infections) and thereafter the disease spreads during thegrowing season. It therefore follows that the occurrences of the diseasein summer would be reduced if a means for combating the overwinteringdisease located in the buds were established.

Attempts have been made in the past to establish a process foreffectively combating overwintering mildews (fungi) but no treatment sofar proposed has achieved any positive degree of commercial usage orsuccess, or even general approval. Thus the treatment of overwinteringinfected buds and apple rootstocks of apple trees usingdinitro-ortho-cresol (DNOC) emulsified in petroleum-oil was attempted,with little success, in the years 1954 to 1961. Results are reviewed inan article by Moore, Bennett and Burchill entitled "Further Studies ofthe influence of oil-emulsion sprays on bud infections of apple mildew".(Report of the East Malling Research Station for 1961, pages 97 to 100).Since that time little further work appears to have been done oninvestigating methods for combating overwintering mildew.

In so far as conventional mildew control methods are concerned, that isthe spraying of actively-growing vegetation, it is known that certainsurface active agents are anti-fungal in their own right when sprayedonto the foliage of actively growing plants. Thus in the CanadianJournal of Botany 42, (1964), page 1335 there appears an article by F.R. Forsyth entitled "Surfactants as fungicides" which shows that surfaceactive agents are fungistatic. Again in Annals of Applied Biology(1963), 52, pages 45 to 54 appears an article entitled "GreenhouseEvaluation of Chemicals for the Control of Powdery Mildews" by Kirby andFrick, similarly pointing out the achievement of fungal disease controlusing substances having surface active properties. These are but two ofmany references showing that surface active agents per se arefungicidal. In addition, the literature on the subject of mildew controlincludes many references to the use of fungicidal substances well knownin the art, either alone, or in conjunction with surface active agentsfor this purpose. None of these treatments, however, has beensuccessfully applied to combat overwintering mildew, and no doubtfailure of the overwintering DNOC/oil treatments referred to above musthave played some part in dissuading researchers from attempting to applyestablished mildew-active materials to overwintering mildew situations.Indeed the small amount of recent research published has pointed awayfrom there being considered any value in the latter approach. Thus ithas recently been shown by E.L. Frick and R.T. Burchill (Plant DiseaseReporter Volume 56, No. 9 September 1972) that substantial eradicationof apple powdery mildew from infected buds of apple trees was obtainedwith applications in the dormant season of mixtures of methyl esters offatty acids or mixtures of fatty alcohols. Substantially normal shootgrowth occurred in the following spring. The aforesaid mixtures ofesters or alcohols were known to act as so-called "chemical pruningagents", more especially as sucker growth inhibitors in tobacco plantsand ornamentals either alone, or in conjunction with other chemicals, asreported in U.S. Pat. Nos. 3,340,040; 3,326,664; and 3,438,765 and hencewere known bud penetrants.

It has now been found, surprisingly, that other chemical substances maybe used to combat overwintering mildews (fungal diseases) and that theuse of these substances has the advantages that it involves less risk ofundesirable damage (phytotoxic effects) occurring in the treated trees.For example they are less likely to kill off healthy buds.

By the term "tree" in this specification is intended any plant, cane,vine, shrub, bush, tree or other vegetation which is ornamental orproduces an edible crop, ornamental blooms, or useful substances.Examples of crop-producing trees are fruit trees, such as apple, peachand pear trees. Examples of ornamental plants are roses. Examples ofuseful-substance producing trees are rubber trees.

Accordingly the present invention provides a process for combatingoverwintering fungal disease comprising applying to ornamental, ediblefruit producing, or useful substance producing, plants, bushes, shrubsor trees, whilst in, or approaching, a dormant phase, an effectiveanti-fungal amount of a composition comprising a substance havingsurface active properties.

The advantage of overwintering treatments, for example the treatment ofapple trees to combat apple powdery mildew when the trees are dormant,or near dormant, is that if a substantial reduction of the mildewinoculum (e.g. spores and mycelium) can be secured, then the amountavailable to spread the disease in the following spring is diminished,and since the incidence of disease is lessened this in turn allows areduction in the frequency or dosage of conventional fungicidetreatments actually made in the spring and summer. There is also adiminishment of the need for removal of diseased tissues by mechanicalexcision, or pruning, which are time-consuming and costly operations.Although, as has been previously mentioned, surface active agents areper se fungicidal, they are used in practice as adjuvants for chemicalsubstances of proven fungicidal efficacy rather than as fungicidesthemselves. Reasons for this include the fact that used alone they tendto produce either an unacceptable degree of phytotoxic damage toactively-growing trees or unacceptably low degrees of mildew control. Inthe situation in which the plant or tree is in, or approaching, adormant phase, however, it has been found, surprisingly, that higherrates of surface active agents can be applied without causingunacceptable damage to the tree, especially the buds thereof, and at thesame time producing a mildew-combating effect.

The invention process combats, in particular, overwintering powderymildew diseases and, for example, is effective against Podosphaeraleucotricha in apple tree buds.

In one preferred aspect, therefore, the invention provides a process forcombating the overwintering disease Podosphaera leucotricha in appletrees which comprises spraying the trees whilst in, or approaching, adormant phase with an effective amount of an aqueous solution,dispersion or emulsion containing at least 0.5% by volume of a substancehaving surface active properties.

The invention process, however, may also be used to combat otheroverwintering fungal diseases such as, for example, downy mildewdiseases, Dibotryon, Fabraea, Taphrina, Nectria cankers, and Rustdiseases. These diseases may occur on, for example, trees, shrubs, vinesor canes.

Particular examples of particular trees and shrubs, and fungal diseaseswhich affect them which may be combated by the invention process are asfollows:

    ______________________________________                                        "Tree"            Disease                                                     ______________________________________                                        Apple           Podosphaera leucotricha                                       Pear            Podosphaera leucotricha                                       Peaches         Taphrina deformans                                            Vine            Plasmopara viticola                                           Rubber          Oidium heveae                                                 Roses           Sphaerotheca pannosa                                          Vine            Uncinula necator                                              ______________________________________                                    

The treatment may be effected in a variety of ways. Preferably the treeis sprayed with a liquid containing a substance having surface activeproperties, but dusting with a powdered formulation containing orconsisting of a substance having surface active properties may also beemployed, as may the application of foams containing a substance havingsurface active properties.

The treatment of the tree is effected whilst the tree is in a dormantphase, or when it is approaching a state of dormancy, that is whenactive growth has ceased and the leaves have either fallen off the treeor are about to fall off. Preferably, therefore, treatment is effectedin the Autumn, or during Winter, but it may also be carried out nearerthe Spring, and even up to the stage just before the buds commence toburst. Within these stages of approaching dormancy and actual dormancyany number of treatments may be carried out. The occasion, and numberof, treatments may therefore be varied for optimum effect depending uponthe type of tree and species of fungus being combated.

The concentration of the substance or mixture of substances havingsurface active properties in the composition used to treat the tree mayvary within wide limits and will depend upon a number of factorsincluding the need to obtain a useful effect and the obvious requirementof mitigating harmful effects, that is phytotoxic effects, which mightresult, in an extreme case, in damage to, or death of, the buds forexample. A further factor is the rate of application, that is the actualvolume of composition applied. Thus if high volumes are used a lowerconcentration of substance having surface active properties may bepresent in the composition used for treatment, whilst if low volumes areapplied a higher concentration of the surface active substance can bepresent in the composition. In general at least 0.5% by volume of thesubstance having surface active properties should be present in thecomposition, the remainder of which is constituted by a solid or liquidcarrier. In an extreme case the substance having surface activeproperties may be used per se, that is without dilution, but, by way ofexample only, the composition may contain, as an upper limit, from about10% to 20% by volume of the substance having surface active properties.Preferred compositions contain about 5% by volume of surface activeagent and are sprayed onto trees in sufficient amount to wet thebranches and tree generally. Water is a preferred liquid diluent. It maybe used alone or admixed with an amount of an alcohol containing from 1to 4 carbon atoms.

When the composition is a liquid, as is preferred, and this is appliedby spraying, a wide variety of spraying techniques may be employedincluding the use of simple knapsack sprayers with nozzles and jets, andthe use of motor-driven sprayers which are hydraulically operated orair-assisted, e.g. to blow a mist, and these may be carried by anoperator or be mounted on wheels and, if desired, be self-propelled ortowed. Aerial spraying techniques may also be used. Thus the tree may besprayed from above and below the branches, or at branch level, or at acombination of levels and spray booms fitted with a plurality of spraynozzles may be employed for this purpose. Preferably the entire tree istreated but, if desired, selected branches only may be treated. As analternative to spraying, a liquid composition comprising a substancehaving surface active properties, may be applied in the form of a foam.Such methods of foam-application are advantageous in that they achieve ahigh application rate since the foam adheres to the branches of thetree.

The surface active agent, that is the substance having surface activeproperties, may be cationic, anionic, or non-ionic in character; or itmay be a mixtrue of one or more surface active agents. If such a mixtureis used it will normally comprise either an anionic or cationic agent inadmixture with a non-ionic agent, or a mixture of two, differentnon-ionic agents, but "amphoteric" surface active agents, that iscompounds of mixed anionic-cationic structure may be used. Suitableagents of the cationic type include, for example, long chain aminecondensates with ethylene oxide, quaternary ammonium compounds, forexample, cetyltrimethyl ammonium bromide. Suitable agents of the anionictype include for example soaps, for example hard, soft and amine soaps,salts or aliphatic monoesters of sulphuric acid, for example sodiumlauryl sulphate, salts of sulphonated aromatic compounds, for examplesodium dodecylbenesulphonate, butyl-naphthalene sulphonate, a mixture ofthe sodium salts of diisopropyl -- and triisopropyl-naphthalenesulphonic acids, and sodium salts of N-alkylated-N-fatty acid tauratsand isethionates, and sodium salts of long chain sulphonateddicarboxylic acids. Suitable agents of the non-ionic type include, forexample, the condensation products of ethylene oxide with fatty alcoholssuch as oleyl alcohol or ceryl alcohol, or with alkyl phenols such asoctylphenol, nonylphenol, and octylcresol. Other non-ionic agents arethe partial esters derived from long chain fatty acids and thecondensation products of the said partial esters with ethylene oxide,the lecithins, and polyoxyethylene ethers of mixed partial fatty acidesters of sorbitol anhydrides.

Suitable specific surface active agents which may be used in theinvention process are set out below in Table I. In the left hand columnthere is given the Trade Mark by which the product is known whilst inthe right hand column is presented as accurate as indication as ispossible of its chemical constitution. The exact chemical nature andmake-up of some of the surface active agents mentioned is not known.

                                      TABLE I                                     __________________________________________________________________________    No.                                                                              Trade Mark    Chemical Constitution                                        __________________________________________________________________________    1  "AGRAL" 90    Is a mixture of 90% Lissapol                                                  NX (see below) and 10%                                                        methylated spirit (methanol).                                2  "AEROSOL" OT 75                                                                             Is a 75% solution of sodium                                                   dioctylsulphosuccinate in                                                     alcohol/water. The alcohol is                                                 believed to be isopropanol.                                  3  "TWEEN" 20    Polyoxyethylene Sorbitan                                                      monododecanoate.                                             4  "TWEEN" 80    Polyoxyethylene Sorbitan mono                                                 (1-octadecanoate).                                           5  DDAB          Didecyldimethylammonium bromide.                             6  "LUBROL" L    A condensate of 1 mole of nonyl                                               phenol with 13 molar proportions                                              of ethylene oxide.                                           7  "LUBROL" APN 5                                                                              A condensate of 1 mole of nonyl                                               phenol with 51/2 moles of ethylene                                            oxide.                                                       8  "LISSAPOL" NX A condensate of 1 mole of nonyl                                               phenol with 8 moles of ethylene                                               oxide.                                                       9  "RENEX" 30    A branched chain tridecyl                                                     alcohol with 12 moles of ethylene                                             oxide.                                                       10 "LUBROL" W    A condensate of a mixture of C.sub.16                                         to C.sub.18 alcohols with 17 moles of                                         ethylene oxide.                                              11 "BRIJ" 35     A condensate of dodecyl alcohol                                               with 23 moles of ethylene oxide.                             12 "ETHYLAN" D259                                                                              A condensate of C.sub.12 to C.sub.15 alcohol                                  alcohols with 9 moles of                                                      ethylene oxide.                                              13 "TRITON" X100 A condensate of 1 mole of octyl                                               phenol with 9 to 10 moles of                                                  ethylene oxide.                                              14 "TERGITOL     Sodium heptadecyl sulphate                                      ANIONIC" 7                                                                 15 "PLURONIC" L64                                                                              A polyoxypropylene block copolymer                                            condensed with ethylene oxide.                               16 "ARYLAN" PWS  An amine salt of dodecylbenzene                                               sulphonic acid.                                              17 "GAFAC" PE 510                                                                              Complex mixtures comprising                                                   mono- and di-esters of ortho                                                  phosphoric acid.                                             18 "ETHOMID" HT60                                                                              Condensate of N,N-substituted                                                 fatty acid amides with 50 moles                                               of ethylene oxide.                                           19 "ARQUAD" 2C75 Dicoco-dimethylammonium                                                       chloride.                                                       "SYNPERONIC" 16                                                                             A mostly saturated straight                                                   C.sub.12 - C.sub.15 alcohol condensed                           admixed with  with 16 moles of ethylene oxide                              40%                                                                              "SYNPERONIC" B113                                                                           A C.sub.11 alcohol condensed with                               (1:1 mixture ratio)                                                                         3 moles of ethylene oxide                                    40%                                                                                             water - 20%                                                 __________________________________________________________________________

The above surface active agents are referred to in McClutcheonsDetergent Annual published yearly by the Allured Publishing Company ofNew Jersey, U.S.A., which lists the manufacturers of the products.

Particularly preferred surface active agents are those numbered 1, 2, 7,9, 10 and 19 in the above table. Thus a particularly preferred class ofnon-ionic surface active agents is constituted by the polyetheralcohols, especially condensates of alkyl phenols or straight orbranched chain fatty alcohols with from 3 to 50 moles of ethylene oxide.In these condensats preferably 1 mole of the alkyl phenol is condensedwith from about 3 to about 9 moles of ethylene oxide. The products knownby the Trade Marks "Agral" 90, "Lissapol" NX and "Lubrol" APN5 areespecially preferred surface active agents of this type.

A further class of non-ionic surface active agents is constituted byesters of polyhydric anhydrides and fatty acids condensed with alkyleneoxides. Within this class fatty acid esters of sorbitan condensed withfrom about 3 to about 80 moles of ethylene oxide are preferred,especially the products known by the Trade Mark "Tween", such as, forexample "Tween" 20 and "Tween" 80.

Surface active agents which are relatively non-toxic to plants andmammals are preferred, as are those which can be shown to be readilybiodegradable, that is broken down in the environment to known,harmless, chemical substances. Especially preferred are surface activeagents appearing on a list approved by the Environmental ProtectionAgency of the U.S.A. for agricultural usage.

Preferred anionic surface active agents include compounds withhydrophilic groups located towards, or at, the middle of hydrocarbonchains. Salts, for example alkali metal salts, of dialkylsulphonateddicarboxylic acids are especially preferred, a specific example beingsodium dioctyl sulphosuccinate.

Preferred cationic surface active agents include alkyl or alkylarylderivatives of aliphatic or aromatic amines, especially quaternaryammonium halides. Specific examples are didecyldimethyl ammonium bromideand dicocodimethylammonium chloride.

The composition used in the process of this invention, may, in additionto a substance having surface active properties, contain an effectiveamount of an anti-fungal substance and this may be any known substancehaving anti-fungal properties. Preferred anti-fungal substances arethose haivng activity against the fungal diseases which infect trees, ashereinbefore defined, or which, by virtue of having a different or morepotent spectrum of activity, are complementary to the activity displayedby the surface active agent. Suitable fungicides for example, includethat known by the common name ethirimol(2-ethylamino-4-methyl-5n-butyl-6-hydroxy pyrimidine - disclosed andclaimed in British Pat. No. 1182584) and the pyrimidine sulphamateesters disclosed and claimed in British Patent Application No. 44401/71.

The surface active agent may be used as such but is preferablyformulated into a composition by admixture with a carrier, which may bea solid or liquid substance.

The compositions are preferably in the form of liquid preparations to beused as sprays, and are generally solutions, dispersions or emulsionscomprising the surface active agent.

The aqueous solutions, dispersions or emulsions may be prepared bydissolving, dispersing or suspending the surface active agent in water,or a mixture of water and an alcohol containing from 1 to 4 carbonatoms. However other liquids, for example organic solvents, may be used,either alone, that is without water being present, or admixed withwater.

The compositions to be used as sprays may also be in the form ofaerosols wherein the formulation is held in a container under pressurein the presence of a propellant such as fluorotrichloromethane ordichlorodifluoromethane.

By the inclusion of suitable additives, for example for improving thedistribution, adhesive power and resistance to rain or treated surfaces,the different compositions can be better adapted for the various usesfor which they are intended.

The compositions which are to be used in the form of liquids, forexample aqueous solutions dispersions or emulsions, are generallysupplied in the form of a concentrate containing a high proportion ofthe surface active agent, the said concentrate to be diluted with waterbefore use. The concentrates are often required to withstand storage forprolonged periods and after such storage, to be capable of dilution withwater in order to form aqueous preparations which remain homogeneous fora sufficient time to enable them to be applied by conventional sprayequipment. They may therefore contain adjuvants of known kind to impartsuch properties to them.

The concentrates may conveniently contain from 10-95% and generally from25-60% by weight of the active ingredient or active ingredients (if afungicide is also included). When diluted to form aqueous preparations,such preparations may contain varying amounts of the surface activeagent depending upon the purpose for which they are to be used, but anaqueous preparation containing from about 0.5% by volume, or more, ofthe active ingredient may, for example, be used.

EXAMPLE 1 Apple Powdery Mildew Eradicant Tests

Apple seedlings, 3" to 5" tall, each with 4-6 leaves were inoculatedwith apple powdery mildew (Podosphaera leucotricha) conidia by shakinginfected plants over them and allowing the conidia to settle. Five orseven days after inoculation the treatments were applied using a spraygun or air brush. Three or four replicate plants were used for eachtreatment.

Assessments were made visually of the percentage leaf area infected withapple powdery mildew at intervals after application.

The results are shown for two tests in Table II below. They indicatethat the surface active agents alone are somewhat more active againstthe fungus and cause less phytotoxic damage than a chemical pruningagent containing fatty alcohols.

The active chemicals were, for the purpose of these tests, formulated bymixing or dissolving them in water, or a mixture of water and a loweralcohol containing from 1 to 4 carbon atoms.

                                      TABLE II                                    __________________________________________________________________________    Treatment and Rate                                                            in spray on a                                                                            Test 1 (applied 6.12.72)                                                                    Test 2 (applied 24.1.73)                             percentage volume/                                                                       % Mildew                                                                           Phytotoxicity                                                                          % Mildew                                                                           Phytotoxicity                                   volume basis                                                                             6 days                                                                             2 days                                                                            6 days                                                                             6 days                                                                             1 day                                                                             2 days                                                                            6 days                                  __________________________________________________________________________    Offshoot T 7.9%                                                                          70   3   3    5    3   4   4-5                                     Offshoot T 4.8%                                                                          90   2   3    10   0   1   4                                       Offshoot T 1.6%                                                                          90   2   2                                                         Agral 90 5%                                                                              60   2   3    0    0   2   3                                       Aerosol OT 75 5%         0    0   2   2                                       DDAB 5%                  0    3   5   5                                       Untreated  100  0   0    100  0   0   0                                       __________________________________________________________________________     Notes                                                                         (1) Rates are percentage product in spray                                     (2) Days refer to time of assessment - number of days after treatment was     applied                                                                       (3) In tests 1 and 2, treatments were applied using an Aerograph MP spray     gun.                                                                          (4) Agral 90 is a non-ionic wetter                                             (5) Aerosol OT 75 is an anionic wetter                                       (6) DDAB (didecyldimethylammonium bromide) is a cationic wetter.              (7) Phytotoxicity scale:                                                      0 - no damage                                                                 1 - very slight damage                                                        2 - slight damage                                                             3 - moderate damage                                                           4 - severe damage                                                             5 - plant killed                                                              (8) "Offshoot" T is a commercially available chemical pruning agent           containing fatty alcohols. (See page 26).                                

EXAMPLE 2

This Example illustrates the activity of surface active agents when usedalone and in conjunction with a fungicide to combat overwintering applemildew disease (Podosphaera leucotricha). Comparison is made with othe,published, chemical treatments for combating this disease. The actualtechnique usd in the field in the UK is set out below.

Treatments comprising four or five replicate plots were used and thechemical formulations, solutions, emulsions or dispersions of the activechemical or chemicals in water, or water plus a lower alcohol of 1 to 4carbon atoms, were applied as high volume sprays beyond the point atwhich the liquid commenced to run-off the trees. This was approximatelyequivalent to a rate of application of 200 gallons per acre. The treeswere Cox's Orange Pippins heavily infected with mildew and they weresprayed during the dormant period after all the leaves had fallen to theground.

Each "plot" was a 1 to 2 meter long terminal section of a branch whichpossessed from 40 to 200 buds. At the time of spraying the numbers ofvisibly healthy buds on the one hand, and of visibly mildew-infectedbuds on the other, were recorded for each plot.

In the following spring (May 17th - 24th, 1973) the numbers of fruit andvegetative buds visibly infected with mildew (i.e. the number of primaryinfections) was observed and recorded for each "plot", together with thetotal number of growing buds (fruit and vegetative) for each plot. Theresults are presented in the Table III below. In this table the lefthand column states the nature of the chemicals used and the percentageamount of the chemical in the actual spray applied (N.B. on a volumebasis for surface active agents and on a weight basis for fungicidalsubstances). In subsequent columns the figures given are mean numbers ofmildew-infected buds per treatment expressed as a percentage of thenumber of mildewed buds in untreated plots as observed and recordedbetween 17th and 24th May 1973.

There was no obvious damage caused by the treatments and they had noeffect upon the total number of growing buds. Some of the treatmentscaused slight delay in bud-burst; this is not considered a disadvantageand could even be an advantage in some situations by avoiding a risk offrost damage.

                                      TABLE III                                   __________________________________________________________________________    Chemical Treatment                                                                           Season and Date of Spray Application                           (Water containing                                                                            Single Autumn or Winter                                        5%, by volume, of                                                                            1972              Single Spring 1973                           the surface active                                                                           Application       Application                                  agent)         29 Nov                                                                              13 Dec                                                                              26 Jan                                                                              15 Mar                                                                              20 Mar                                 __________________________________________________________________________    Agral 90 (5% by volume)                                                                      64    15    0     25    0                                      Aerosol OT 75 (5% by                                                                         --    0.3   0     --    --                                      volume)                                                                      Tween 20 (5% by volume)                                                                      --    35    --    --    --                                     Agral 90 + Ethirimol                                                                         --    0     0     --    --                                     (5% by volume) (1% by                                                          weight)                                                                      Aerosol OT 75 + Ethirimol                                                                    --    0.6   --    --    --                                     (5% by volume) (1% by                                                          weight)                                                                      Tween 20 + Ethirimol                                                                         --    0.9   --    --    --                                     (5% by volume) (1% by                                                          weight)                                                                      DDAB + Ethirimol (5% by                                                                      --    --    0     --    --                                     volume) (0.1% by weight)                                                      DDAB + Ethirimol                                                                             --    --    0     --    --                                     (5% by volume) 1.0% by weight)                                                DDAB + Ethirimol                                                                             --    --    0     --    --                                     (3% by volume) (1% by weight)                                                 "Offshoot" T   74    70    20    68    50                                     (7.9% by volume)                                                              "Offshoot" O   --    --    31    --    --                                     (11.1% by volume)                                                             Untreated*     100   100   100   100   100                                    *The actual percentage amount                                                 of mildew on the untreated                                                    trees was      46.3  33.9  5.7   46.3  14.8                                   __________________________________________________________________________     N.B.                                                                          The above valued are not directly comparable horizontally since different     sites were sprayed at different dates.                                   

"Offshoot" 0 comprises 45% of methyl esters of C₆ to C₁₂ fatty acids and55% of inert ingredients. The make-up of the esters is believed to be asfollows: methyl hexanoate 4%; methyl octanoate 56%; methyl decanoate38%; methyl dodecanoate 2%. The inert ingredients are believed tocomprise polyoxyethylene (20) Sorbitan monododecanoate ("Tween 20") 45%and water 10%.

"Offshoot" T comprises 63% of C₆ to C₁₂ fatty alcohols and 37% of inertingredients. The makeup of the fatty alcohols is believed to be n-hexylalcohol 0.5%; n-octyl alcohol 42%; n-decyl alcohol 56%; n-dodecylalcohol 1.5%. The inert ingredients are believed to comprise a "Tween"wetting agent.

EXAMPLE 3

In mid-autumn selected branches of apple (variety Jonathan) trees weresprayed with aqueous solutions of a number of surace active agents.There were six trees, and branches on each tree were subjected to eachspray treatment. The experiments were conducted at two sites (site A andsite B) and an assessment was made in the late spring of the numbers ofhealthy buds on the one hand, and the number carrying the powdery mildewdisease Podosphaera leucotricha on the other.

The results are given in Table IV below, in the first column of which ispresented the commercial name of the surface active agent used(reference should be made to Table I hereinbefore for the chemicalnature of the surface active agent). The second column statesconcentration of the surface active agent used and the third and fourthcolumns give the percentage number of infected buds observed at springassessment.

                                      TABLE IV                                    __________________________________________________________________________    Surface Active                                                                          Concentration                                                                         Percentage Number                                             Agent   in percentage                                                                         of Diseased buds                                             TRADE MARK                                                                             volume  Site A    Site B                                            __________________________________________________________________________    AGRAL 90  5       22.00     6.67                                              LUBROL APN 5                                                                            5       16.33     2.93                                              LUBROL L  5       39.67     11.18                                             RENEX 30  5       31.33     5.83                                              AEROSOL OT75                                                                            5        5.67     1.14                                              ETHOMID HT60                                                                            5       45.67     22.01                                             ARQUAD 2C75                                                                             5       20.00     1.07                                              LUBROL W  5       44.33     12.43                                             Untreated Control 53.00     23.25                                                                    54.00     22.07                                          "               55.00     20.89                                             __________________________________________________________________________

We claim:
 1. A process for combating overwintering powdery mildew intrees comprising spraying said trees while in a dormant phase with anantifungally effective amount of an aqueous composition consistingessentially of water and at least 0.5% by volume of an active ingredientwhich is a surface active compound, said surface active compound being apolyether alcohol which is a condensate of (a) 1 mole of nonyl phenol,octyl phenol, octyl cresol, tridecyl alcohol, dodecyl alcohol, a mixtureof C₁₆ to C₁₈ alcohols or a mixture of C₁₂ to C₁₅ alcohols, with (b)3-50 moles of ethylene oxide.
 2. A process according to claim 1 whereinthe polyether alcohol is a condensate of monyl phenol with from 3 to 9moles of ethylene oxide.
 3. A process according to claim 1 wherein thetrees are apple trees which are sprayed against Podosphaera leucotricha.4. A process according to claim 1 wherein the composition additionallycontains a minor amount of an alcohol containing from 1 to 4 carbonatoms.